Dynamic magneto-optic coupling in a ferromagnetic nematic liquid crystal

TL;DR

This paper investigates the dynamic magneto-optic coupling in a ferromagnetic nematic liquid crystal, revealing how dissipative cross-coupling influences the response and providing a macroscopic theoretical framework.

Contribution

It demonstrates the experimental and theoretical analysis of magneto-optic coupling in ferromagnetic nematic liquid crystals, highlighting the role of dissipative cross-coupling between order parameters.

Findings

The magneto-optic response is significantly affected by dynamic cross-coupling.

The cross-coupling coefficient is comparable to the rotational viscosity.

Experimental results align with a macroscopic theoretical model.

Abstract

Hydrodynamics of complex fuids with multiple order parameters is governed by a set of dynamic equations with many material constants, of which only some are easily measurable. We present a unique example of a dynamic magneto-optic coupling in a ferromagnetic nematic liquid, in which long-range orientational order of liquid crystalline molecules is accompanied by long-range magnetic order of magnetic nanoplatelets. We investigate the dynamics of the magneto-optic response experimentally and theoretically and find out that it is significantly affected by the dissipative dynamic cross-coupling between the nematic and magnetic order parameters. The cross-coupling coefficient determined by fitting the experimental results with a macroscopic theory is of the same order of magnitude as the dissipative coefficient (rotational viscosity) that governs the reorientation of pure liquid crystals.